1. Field of the Invention
The present invention is related to designing for a power semiconductor, and especially to a power semiconductor formed by using the basic materials including two metal plates and a ceramic plate.
2. Description of the Prior Art
The traces of electric power and electron can be seen in the fields of utility in industry, power systems, traffic, commerce, aviation, computer communication and military affairs, in the field of electric power and electron, power semiconductor elements are often used to achieve various requirements. As shown in FIG. 1 which is a schematic view of a normal structure of power semiconductor, the power semiconductor is provided therein with a silicon chip 10 made of silicon (or germanium), the silicon chip 10 has electric connecting pins 11 extending outwards therefrom, and is sealed with a non electric conductive epoxy resin layer 20 (called as sealing or pouring of plastic), and the electric connecting pins 11 are used to form connecting of the entire power semiconductor with an electric circuit.
In practical operation of the power semiconductor, high temperature can be generated to thereby influence the state of operation of the power semiconductor; and thereby a normal power semiconductor is provided in advance with a copper made heat conducting plate 30 on an surface of the epoxy resin layer 20, the heat conducting plate 30 is contacted with the silicon chip 10, the conducting plate 30 can increase the heat exchange rate with air, so that an object of reducing the temperature of the power semiconductor can be achieved.
However, when the heat generated in operation of the power semiconductor is transmitted to the outer epoxy resin layer 20, by virtue that the epoxy resin layer 20 has inferior heat conductivity, after using for a long period, the epoxy resin layer 20 will absorb heat energy and store/seal the heat energy which is hard to dissipate in the power semiconductor; this is subjected to inducing overheating of the power semiconductor that renders the latter unable to operate normally, and thereby reduces the life of use of the power semiconductor.
The heat conductivity of a normal epoxy resin layer 20 is 0.0032, as to the heat conductivity of a kind of non electric conductive material, the material of the normal epoxy resin layer 20 is not excellent in its efficiency of heat conducting; in other words, when the amount of heat generated by the silicon chip 10 is constant, the heat conducting efficiency of the power semiconductor is changed in dependence on the volume of the epoxy resin layer 20 and that of the heat conducting plate 30; if the epoxy resin is substituted by ceramic (the heat conductivity of the ceramic is about 25 times of that of the epoxy resin), the efficiency of heat conducting can be increased, and the power semiconductor is easier to scatter heat.
More over, if the epoxy resin is substituted by ceramic, the ceramic can be shaped firstly and then combined with metallic heat conducting plates by a high temperature sintering technique; in this way, the process of manufacturing can be different from the conventional one which needs complicated process and equipment for plastic sealing (called as sealing or pouring of plastic), the process of manufacturing can be simplified, and the efficiency of automation production can thus be increased.
Additionally, the above stated conventional power semiconductor scatters heat by means of a single exposed heat conducting plate 30, if two mutual opposite sides of the power semiconductor are provided each with a heat conducting plate, the area of heat sinking can be increased to twofold, thus the efficiency of heat sinking can be largely increased.